Telephone lock-out.



W. L. CAMPBELL. TELEPHONE LOCK-OUT. APPLICATION FILED FEB. 26, I097.

Patented May 13, 1913.

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WILSON I... CAMPBELL, or cnxcaeo, ILLINOIS, Assrenon, BY MESNE ASSIGNMENTS,

'ro rmsr rnus'r AND SAVINGS BANK, TRUSTEE, or CHICAGO, ILLINOIS.

TELEPHONE LOCK-OUT. I

Specification of Letters Patent.

Patented May 13, 1913.

Applichtion filed February 26, 1907. Serial No. 359,05.

To all wlioni, it ma z concern I.

Be it known that 1, WILSON L. CAMPBELL,

and resident of Chicagmfiook county, Illinois, hare invented a new and, usean Improvement in Telephone Locl -()uts, of which the following is a specification.

My invention relates to automatic telephone exchange systems, and more particularly to automatic party line systems in which means are employed for preventing interference between subscrlberson the same line.

Inceitain respects my invention is in the 1 nature of an improvement on the party line system disclosed in application Serial No.

" 343,566, filed November 15, 1906, by C. J.

Erickson for improvement in party linetelephone systems. In said prior application a mechanical locking arrangement is.

employed for positively locking the calling subscribers dial against operation should he attempt .to use it after some other subscriber on the same line has entered into conversation with a third subscriber on the,

same line, or with a subscriber on any other line. Also, in the said prior application the operating his dial after the party line is in the possession of another subscriber thereon, and before the called subscriber answers;

' the provision of a-dialloclting arrangement closed and claimed.

a, The accompanyin drawing is a diagram showing two lines #110 and #210) connected throu h a central station, either or both 'of whic may be party lines, but only line #110 at the left being shown as such.

At said-central ofiice there is also shown a.

central battery B having its positive termimu preferably grounded at G. Said line.

# llq'is shown provided with two substae tiousKA and A) that are bridged across the line conductors, and the other line #210 is also provided with a substation C. The

line -#110 is shown connected through the first-selector D and connector E with the second line #210, which latter alias bridged across it a first-selector-switch F. All ofgrounded simultaneously. When the switchhook is down, the cam-arm 5 engages the spring 10, thereby bridging the ringer 11 in series with the condenser 11 across the line. l urthermo-re, when the switch-hook is down the said cam 5 disengages the springs 12, 13 and 14, thus breaking the local circuit which includes in series the primary Winding 15, transmitter 16 and local battery 17,

and disconnecting the substation locking relay 39 from one side of the line.

The substation ground circuit is normally broken between the grouudsprings 18 and 10 by the cam-armfij but when said springs are together, ground connection is then provided to the ground post 20 and to the release spring 7, as'is usually the case in-tel-ephones of this type. The said substation comprises the usual induction-coil 21 having the primary winding 15'and secondary winding 22. Being an automatic substation it is provided with the usual vertical androtary impulse springs 23 and 2 1. Said substation is, of course, provided with a dial (not shown) which is secured to the shaft 25, together with the locking dog 26. Furthermore, there is a locking cam 27 that locks the dog 26, while the receiver is on the switch-hook, to prevent a rotation of the dial. For operating the impulse springs 23 and 24 the substation is provided with an impulse wheel 28 that is secured to the shaft 25, which impulse wheel carries on its periphery the so-called vertical impulse teeth 29 and one rotary impulse tooth 30. The said impulse teeth are so arranged that when the dial is rotated the impulse springs 23 and'24 are not carried into contact with the ground post but as the dial returns, first the vertical teeth engage the vertical impulse spring 23, and after they have com- 15 pleted their work the rotary impulse tooth 30 operates the rotary impulse spring 24. In this operation the subscribers vertical line conductor 31 is first given a number of ground impulses, and then the rotary line 20 ccnductor 32 is given one ground impulse. It will be noticed that as long as the dial is out of normal position the construction is such that the dog 26 permits the second- "ary circuit springs 33 and 34 to separate,

thus preventing the impulses that are delivered to either line conductor from passing to the other. The substation is further provided with a signaling device that comprises the push button spring 35 which normally engages the contactpoint 36; but when the button 37 is pressed the spring 35 engages the contact point 38, whereby the vertical line conductor 31 may be grounded. In addition, the substation is provided with a lock-out relay 39 which, when the receiver is removed, is connected between the rotary line conductor 32 and ground Gr through the springs 40 and 19. The said relay is provided with an armature 41 pivoted at 40 the point 42, and at its non-pivoted end said armature has a hook. This hook is adapted to engage an eye 43 on the locking dog 26, when the lock-out relay becomes energized, thereby locking the said dog in normal position; and since said dog is rigidly connected to the dial the latter is operation by the subscriber. The armature 41 is retained in normal position by the re tracting spring 44. The first-selector switch shown at D is of the general type described in United States Patent No.'8l5,32l, granted March 13, 1906, to Keith, Erickson 8; Erickson, having some slight modificationsthat is, the rotary side of the line is retained normally open by the switch shaft, instead of being normally closed as is usually the case. It embodies among other details the following well-known devices and circuits: The switch-shaft (not shown) carries the vertical and rotary wipers 45 and 46, respectively, and the private wiper 47. The side switch is well known and comprises the side switch wipers 48, 49, and 51, which may be designated as the vertical, rotary and prialso locked against vate side switch wipers, and the rotary magnet wiper, respectively. The side switch is under the control of the private magnet 52, and in the normal or first position of the side switch the wipers 48, 49, 50 and 51 occupy the contact points 53, 54, 55 and 56, respectively; in the second position they rest on the contact points 57, 58, 59 and 60, respectively, and in the third position the contact points 61, 62, 63 and 64 are engaged by their respective wipers. Through the me dium of the vertical line relay 65, and while the side switch is in first position, the subscriber controls the vertical magnet 66, which latter operates to raise the switch shaft and wipers 45, 46 and 47 vertically.

By means of the rotary line relay 67, and while the side switch is in the first position, the subscriber controls the private magnet 52 and, therefore, the side switch. lVhile the side switch is in second posit-ion the rotary magnet 68, which operates to carry the switch shaft and wipers 45, 46 and 47 in a rotary'direction, is energized. The vertical and rotary line relays 65 and 67, acting conjointly, provide means whereby the subscriber controls the release magnet 68' while the side switch is in the first or second position. It the side switch passes to third position, then, since the selector is of the trunkrelease type, the selector is controlled through the next switch (with which latter a connection is then established) and through the private wiper 47 and by means of the back-release relay 69. The bridgecut-otf relay 70 is provided to open the connection between the line relays 65 and 67 and between said relays and battery B. This is desirable, because if the relays are not disconnected from each other and battery the ringing current for signaling the subscriber may operate either or both of the relays 65 and 67, and thus cause some interference with the switch. It is also desirable to remove the bridge formed through the said relays from across the line to give the voice-currents as clear a path as possible. In addition, the said selector switch is' provided with a private normal relay 71 by means of which the guarding potential at the connector bank is momentarily removed to enable a subscriber to call back on his own line. The switch shaft also carries the normal arm 72which, when the shaft is in normal position, retains the spring 73 out of engagement with the spring 74, thus disconnecting the rotary line conductor 32 from the side switch wiper 49; but when the shaft is-given its first vertical step the springs 74 and 73 come together. terminals of the relay 71 is thecondenser 75, used to improve the talking circuit.

Bridged between the The connector switch E may also be of any suitableor approved type, for instance of the general type described Zia-United States Patent No. 815,176, granted March 13,

1906, to Keith, Erickson & Erickson. ,-The

the same, although there is some material dIfle-rence in the circuits; The connector switch shaft (notrshown) liket-he first-selem torswitch'shaft, carries the line wipers 76 and 77 and the private wiper 7 8. The: con-1 hector-switch is also controlled by the callingsubscriber through the medium "of the vertical and rotary line relays 79 and 80.-

- The vertical line relay directly controls. the

vertical magnet 81, and also the rotary magnet' 82 and ringer relay-83. The ofiice of the vertical magnet 81 isto give the shaft and shaft wipers their vertical motion; and

the rotary magnet- 82 impartsto the shaftand shaft wipers a rotary or circular mo tion. The rotary line relay controls the private magnet 84, which latter, under certain conditions, controls in turn the vertical and rotary magnets 81 and-.82, the release magnet .85, and'also' the sideswitch Wipers 86,87, 88 and 89. Theside switch of-the connector, like the side switch of the firstselector, has a normal or first position, a second position and a. third: position.- The release magnet is. also-controlled by the line relays. 79 and 80, conjointly. By the condensers 90 and 91 the circuit through the connector is divided into two sections; The central otfice'is equipped with a busy-signalingapparatus of any suitable design, as, for example, the one comprising aninterrupter 92 in series with the primary winding 93 of the induction-coil 94, whereby a busy signaling current is induced in the secondary winding 95 of the said coil. The connector switch shaft also carries a normal post arm 96 which, when the connector shaft is 0112' normal, allows the spring 97 to engage-dig;-

. contact point 98, whereby a, busy-signalin the vertical. line is grounded acertain num I and34 andbreaking the contact'betwcencurrent may be transmitted to the calling subscriber when the side switch is in .first position. The calling operation by'whiclrthe subscriber A, for example, would call and signal subscriber C is as follows: To call the number 2l0, wh-ich is assumed to be the number of substation C, the subscriber A at sub static-11 #110-operates his callingdevice in a. suitable manner corresponding to each 9 1102 and 1 07- to the private magnet 52 and "battery lead 101, thence through battery B digit of the called number. each digit ber of times,corresponding to the numerical value of the digit, and then the'rotary-side of the line is grounded .on'ce. The receiver- 2 is, of course, first removed from the switchhook 3, closingfin' contact the springs 33 the springfiO and cam-arm 5, thus removing the'nnger ll from ecrossthe line and closto the ground post 20,,the'nce' to the verti Ical impulse spring 23, vertical line con-. .ductor 31 to the side switch wiper 48', con tact, point 53, through the; vertical line relay 65' to the bridge-cut-ott springsz99; and 100, to the battery lead l0l',t V "tery B 'toground Gr; time that the cal line ,relay'sprlngs 102ml 1.03 are pressed into contact, and an energizing circuit is eachtimeestablished' through ,theverticali springs 1 02-and; 103; to the' private magnet 46 and 47 are raised two steps; The, said -wipers arecarrie'dtoaflcvelwith the contact points'jthat, constitute the terminal of ling the receiver circuit. The first digit be- 6'5 lin g '2, the subscriber atsuhstationA turns i his dial for the-first digit 2,fthereby grounding the vertical line conductor 31 twice, and. "the: rotary tine conductor 32- once upon the =return motion of the dial: Grounding the *vertical line conductor 31 -1twice, as ex- '-'plained, energizes the vertical-line' relay 65 I oi the firstselector. The circuit through the i said vertical line rela'y extends from ground a tam hthe g oun p n 19.31111, 18

vertical line rela 65 is energized the vertimagnet 66. The circuitithrough said'mag; net extends from-ground G to" the relay springs ,104 and 9 105, through the winding 1 of the vertical ma ch66 the'battery lead-j 101, thence throng -bat t ery-,B'-to ground G.

i The vertical magnet 66 bein operated twice,

the first-selector switch sha t and wipers 45 the' trunk-line leading to 1 the connector switch E; Followingthelvertical impulse the rotary impulse spring. 24 is grounded once by the rotary iinpulse tooth 30, thereby grounding the rotary. line conductor 32 once and energizing there "My line relay67. The path "of this energizing circuit is ,from ground. G iilll'OHghI- thQ ground springs 19 and 18 to the ground" post. 20, through the rotary impulse springi24 tolthe rotary line conductor'32, normal springs 74*and 7 3, side switch wiper 49,00ntact point 54 to the rotaryline relay 67, thence to" the' bridge-mt .110

Qofi springs'106, 99 and 100 and to the bat.-

teryllead 101,.thence'through'battery B to ground; G; The rotary line relay, upon energizing, presses the-line='relayspr1ngs 107 and 102 into contact, thereby establishing an energizing circuit through the private mag-= net 52. The current through said magnet passes from ground G through the springsand to ground G. The private magnet. being ener edfor a moinent, the side switch of the first-selector passes to second position,

(it through the contact point 60, side switch 1 wiper 5-1" to the interrupter springs. 108,

. i ing-the circuit through the through battery. B and to v stitute the terminal of magnet 52 when the private wiper 47 strikes ,a. grounded contact, therebylretaining the andmaintainrotary magnet 68. The rotary magnet, by intermittent energizing, causes the shaft wipers to rotate pastthe last busy trunk line. However, as

side switch in-second position soonas the private magnet deenergizes, the

side switch is tripped into third position; or, if there'are no busy contacts "to be passed over, the rotary magnet 68,-as is well known, trips the side switch to third position, when the wipers engage the first trunk line, with the result that as soonas the side switch wipers 48 and 49 engage their respective contacts 61 and 62 the subscribers line is extended to the connector switch E. Also, since the side switch wiper 50'engages the grounded contact point 63, a guarding potential is established at the private wiper 47 for preventing the seized trunk line to the connector E from being molested by' any other switch. This guarding potential also protects the calling line by establishing a guarding potential at the connector bank over the private normal conductor 109. The second digit is called after the subscriber has established connection with the connector E by way of the trunk conductors 110 and 111. The subscriber rotates the dial, as described, for the second digit 1, thereby grounding the "ertical and rotary line conductors 31 and 32, ing of the connector vertical and rotary line relays 79 and 80. The energizing current for this purpose fiowsoverthe following path: from ground G to the vertical line conductor 31 to the side switch wiper 4.8, contact 'point 61, shaft wiper 45 to the trunk conductor 110, through the winding of the vers tical line relay 79 to the-battery lead 101, thence through battery B to ground G. Each time the vertical line relay 79 is energized the-line relay springs 112 and 113 are pressed into contact, and an energizing circuit is established each time through the vertical magnet 81. i The energizing current through the vertical magnet 81 flows from ground G to the springs 112- and 113, rivate magnet springs 114 and 115, side switch wiper 88, cont-act ioint 116 to the vertical magnet 81, to the attery lead 101, thence through battery B to ground G. The vertical magnet 81, each time it is energized, raises rated the terminals of the which causes the energiz-' the shaft and shaft wipers 76, 77 and 78 one step and opposite a level'in which are lothe rotary'line conductorrotary, line relay through the following pathrfrom ground G to the rotary line conductor 32, normal 32 is grounded the springs 74 and 73, side switch wi er 49, con-' tact point 62, through the win ing of the private normal relay 71, shaft trunk conductor '111, ringer relay springs I17 and 118, through the winding ofthe ro- 'tary line relay 80 to the battery lead-101,

thence through battery B and to ground G.

line 210. when wiper 16, i

80 becomes energized The-energizing, of the rotary line relay 80 causes the springs 119 and 112 to come into contact, thereby completing a circuit through the private magnet 84. The path of the energizing current is from ground G to the line, relay springs 112 and 119, through the winding of the private magnet 84 to the bats tery to ground G. The momentary energizing of the private magnet 84 causes the release of the side switch from, first to' second position,

,thus placing the side switch wipers 88 and 89 in contact with the points 120 and 121,

being naught respectively. The last digit the subscriber operates the dial as previously described, grounding the vertical line conductor 31 ten times and the rotary line conductor 32 once. The vertical and rotary line relays 79 and 80 are operated over the previously traced circuits. However, when the line'relay springs 112 and 113 engage each other a circuitis closed through the rotary magnet '82, instead of through the vertical lead 101, thence through batteryB and magnet 81. -The circuit may be traced from ground G to the line relay springs 112 and 113, side switch wiper 88, contact point 120, through the rotary magnet 82 to the battcry lead 101, thence through battery B to ground G.

Each time that the' rotary magnet is energized the rotary armature is attracted and and 78 one step at a time, until the said wipers are carried into engagement with the normal conductors 122, 123 and 124, the first two of which lead to the line of the desired subscriber, whose number is 210. The energizing of the rotary line relay 80 for the last digit completes an energizing circuit through the private magnet 84 which now operates with one of two results, namely the release of the side switch from second sition, or the so-called busy-release of the private magnetsprings 114 and 115,

to third poconnector if the called line is busy. Suppose the former result tooccur, and the side switch to pass to third posit-ion, placing the side switch wipers 86, 87, 88 and 89 in contact with the p oints 125, 126, 127 and 128, respectively. -urthermore, when the side 110 rctatesthe shaft carrying the wipers 76, 77

menses switch passes to third position a guarding potential is established for protecting thecalled line. This potential extends from ground G to the contact point 128, side switch wiper89, to the shaft wiper 78 which engages the private contact of the called.

line. The said engagement of the contact p'oint128 by the side switchwiper 89 closes an energizing circuit through the bridge- -thereby; disconnecting the vertical and roltalg-hnerelays of the first-selector F from ea f cut-ofi relay129 of the first-selector F,

other and from the battery lead. Now,

fi jtoi signal the called subscriber, the calling subscriber presses the signaling button 37,

placing the spring in contact with the substation ground G, thereby energizing the vertical line relay 79. The path of the energizing current extends fromground G {to the contact point 38, spring 35, springs 34 and .33 to the vertical line conductor 31, thence through the connector vertica-l' relay 79, as previously traced, to battery B and to ground G. It will be remembered that the connector side switch has passed from second to third position, and that the side switch wiper 88 is in' engagement with the Q Contact point127, thereby placing the vertical line relay 79 in control of the ringer relay 83 inthe same manner in which the rotary magnet 82 came under the control of the. vertical line relay 79 when the side switch passed from first to second position.

Therefore, when the vertical line relay 79 presses the springs 112' and 113 into contact the ringer relay 83 is energized by a flow of current from ground G to the relay springs 112 and 113, private magnet springs 114 and 11.5, side switch wiper 88, contact point 127 to the ringer relay 83 and to the battery lead 101, thenc through battery B and ,to ground G. The r higer relay, upon energizing, dis-v engages the springs 117 and 118 and shifts the springs 129 and 130, respectively, from the springs 131 and 132 onto the springs 133 113111134. This results in separating the calling subscribers line from thecalled subscribers line and bridging across the line of the laitieri the terminals of the ringer generator A signaling current is, therefore,

sent from the generator H to the ringer reand 180resum'e t eir normal'position'in con-- enerator H. Asv

tact with the springs 131 and 132, respcctively. The subscriber 0, in response to the signal, removes the. receiver 141 from the switch-hook "139,- thereby removing the ,,rin'ger 137 from across his line and bridging instead't-he secondary circuit which includes the condenser 136, receiver 141, secondary winding 142 of the induction-coilll43 and secondary springs-144 and 145. The local transmitter circuit is closed as soon as the springs 146, 147'and 148 engage in contact. The two substations #110 and #210 are now connected over the circuit shown by heavy lines in Fig. 1.

From the preceding it will be seen thata callin line as well as a called line is ro-' tested against interference by a third line by proper guarding potentials at the connector banks. In a party line system like this, however, it becomes necessary to insure to the subscriber who first obtains control of the line the use, ofthe line without molestation until afterhe is through calling.

The means by which I accomplish this com prises the substation loclc out magnet 154 at, substation A. If, after the two subscribers A and C are connected for conversation, as explained, the subscriber at substation A attempts to make use of the line themagnet 154 energizes and locks the subscribers dial, and in this way he -is prevented from operating his telephone and is thus prevented from interfering with the connection that is already established. It will be understood that the magnet 154 does not energize except when another subscriber on the-same linerhas previously obtained control of the line, as already explained Assuming that the SUlJSCl'lbEISA and C are in connection over the circuit mentioned, and that the subscriber A (who occupies the line in common with A) removes his receiver 149 fromthe switch-hook 150, as the receiver rises the magnet 154 is energized. The energizing circuit for the said magnet 154- is established at the instant that the springs 152- and 153 come into contact, provided the selector D has operated so that the switch shaft has permitted the switch shaft springs 74 and 73 to close in contact.

The energizing circuit for the lock-out magnet extends as follows: from grouhd- G through the lockingrelay groundcirciiit springs 157 and 158, through the magnet .154, springs 152 and to the rotary line conductor "32, thence by any one oi the various paths to the non-grounded terminal of battery B. The path by which thecurrent passes from the rotary line conductor 32 to the non-grounded terminal of battery B depends'upon the time at which the sub-,

scriber A attempts to come on the line. If

he does so before the first-selector, side switch has passed from the first position lows: through and 78, side switch wiper 49 and rotary line relay"67, bridge-cut ofl' relay springs 106, 99 and 100 to the battery lead 101. If he comes in when the side switch is in'second position the path to the battery extends from the side switch wiper 19 through the.

vertical line relay 65; and if while the side switch is in third position the path to dongrounded battery is through the private normal relay 71, through the ringer relay springs 117 and 118 and vertical line relay 80 of the connector. When the magnet154 energizes it attracts its armature 155, which armature then engages the eye of the camdog 156; and since the said dog 15.6 is

"rigidly connected to, the shaft upon which the dial is mounted, the subscriber is unable to turn the dial as'long as the said magnet 154 is energized. The construction of the substation (referring to substation A) is such that when the receiver is on the switch hook the cam=6 retains the ground spring '19 away from the locking cam 27, which latter then drops to its normal position, as

indicated at substation C; and in this positionan insulatingtip carried by said cam, 27 falls in front of the angled terminal of the ground sprin 19, whereby the said spring 19 is retained in "engagement with the locking magnet spring 40 While the receiver is on the switch-hook, and even after theswit'ch-hook rises, and until. after the dial is rotated. When the dial is rotated the cam 27, which has been previously raised by the cam-arm 6 of the switch-hook, so as to clear the cam-dog 26 enough to enable the dial to be rotated further raised the pin on the end of the cam-dog 26; at which time the insulating tip on the end of the locking dog 27 clears the angled terminal of the ground spring 19, which 'spring then leaves the locking magnet spring 40 and passes into engagement with the spring 18, from,which connection is made to the ground contact of the push but-v ton 37 and to the ground release spring 7. It will be evident, then, that until the dial has been rotated-it is impossible for the subscriber to send impulses to the linebv either working his switch-hook up and dowh and thereby pressing the release springs together, or by pressing his signaling button.

Therefore, it becomes evident that if the subscriber A comes on theline after the subscriber at substation A has operated the selector D the magnet 154 will lock the dial and prevent him from sending ground impulses to the line conductors 31 and \Vhen the subscriber at substationAlearns that he can make no connection he will, of

course, hang up his receiver, by which op.

eration the springs 152 and 153 are sepa as shown at A, is still rated and the energizing circuit of the magnet 15 1 broken.' Said magnet, upon deenergizing, of course, permits its armature in the substation to its normal condition. aving thus described how a second subscriber on the calling line is prevented from interfering with an established connection, it will be well to point out how a second subscriber on the called line is prevented from interfering with the.connection. It has been described that as soon as the connector completes connection with the desired line, the bridge-cut-off relay 129 energizes and disconnects the line relays of the selector F from each other and from the battery lead. Furthermore; it will be evident that in the connector there is no connection between the main line of the called subscriber and the non-grounded terminal of the battery on the called side of the condensers 90 and 91. Therefore, a second subscriber on a called line may come in on the line and operate his telephone if he chooses; but he cannot interfere with the connection, because the battery. 1

Having thus described the noninterfering feature of my system I will now describe how the calling subscriber destroys the established connection with the called line after he is through talking. Having decided to disconnect, he hangs his receiver 2 upon the switch-hook 3, which latter, upon descending, presses the release springs 7, 8 and 9 into contact. The contact of the said release springs grounds the vertical and rotary line conductors 31 and 32 simultaneously from ground G to the release spring 7, thence through the springs 8 and 9 to the vertical and rotary line conductors,

cal and rotary line relays 79 and of the connector E, whereby the trunk-release springs 159 and 160 are brought into contact, closing a circuit through the release relay 69 of the first-selector D in series with the release magnetof the connector E. The path of the circuit extends from ground G to the-contact point 63, side switch wiper 50, release relay 69, first-selector switch shaft wiper 47, connector trunk-relcasfe springs 159 and 160, release magnet 85 to the battery lead 101, thence through battry B and to ground G. I When the connector release magnet 85 is thus supplied with current it energizes, and as a result the switch shaft and side switchare restored to normal position, thus breaking the connection between the connector switch shaft wipers 76, 77 and 78 and the normal conductors 122, 123 and 124;. The back-release relay 69 of thefirst-selector D, being in the :same circuit with the release magnet 85,

155 to recede from the dog 156, thus restor-.

ground impulses do not reach the thereby simultaneously energizing the vertienergiz'es simultaneously with the latter and --presses the springs 161 and 162 into engage= ment, which in turn closes an energizing circuit through the release 'magnet 68 of; the first-selector 1D; This" circuit' extends "-from ground G through the release relay I fsprings'l6l and Y162, through the winding'.

i '5', otth'e release magnet '68?" to the'battei y-lead 4101, thence through battery-B and to ground G. The' release. magnet 68 thus energized f butall other magnets as well, leaving the apparatus fully restored The calling subscriber thus restores all-switching apparatus which'he Originally brought into use. .To

call any subsoribernot on his own linle,' the calling subscriber will bring about the operation as described; but -a subscriheb like the subscriber at substation A, may; also .call

another subscriber on his i own line,- l For instance, suppose the subscriber-"A" desires to signalxa subscriber occupying the same 7 line as subscriber A. In this-case the callspecial-provision-is made, in the firstselectbt' mswitclr to momentarily remove the. guarding 1 potential established at the connector bank and thus'allow, a subscriber to call back .on his ownuline, Wbem-thelastj rotary 'im-. pulse is sent over the.l 1 ne,theprivatc normal relay 71 becomes energized; thus-the springs 163;.and- 164 disengage and remove the guardingpotential from the connector bank. The impulse'to the rotary line removes the protecting potential which would cause the busy-releaseof the connector, andthe con- 'nector private magnet 84 o crates to re- -scriber at A" recognizes his substation iig lease the side switch to thir position. It is evident, therefore, that a subscriber calling another subscriber on his own line would never get a busy-release.

.Thc subscriber'A having connected the switching apparatus at'the central station with his own iin eyby pressing the signaling button a suitable number of times sends signaling current impulses out on his line,

ringing" the different substation'bells' ich are bridged across the called line. The

nail (two rings,- for instance} and removes his receiver from the switch-hook, and when i the springs 152 and153 enga e,'an. energizing circuit is established t rough the locking relay 154 which operates as explained. Thus it will'be seen at any sub-l scriber may call his own line, inasmuch as i the connector switch E used in this. case will not be automatically released as soon as it engages the multiple line terminal connectmg and called lines are identical;= -bu-t a.

ed with the linefroni which the call came.

The two-subscribers who are-conversing on .lo'c'lji-outrelayv of the thirdsubscribers subscriber has called back upon his own'line, is the same as'in anyother. -instanc ethat is, when one. subscriber has called another subscriber on his own line, .thewcalling subscriber. may release the. switching apparatus by groundmgthe line conductors 31 and 32 -when the; receiver is hung .on the hook,

.s'tation'as-soon as-his switch-hook rises. 'lt ;wil'l.be evident that the release, when a su'b- 5 yenergizing circuitis established through the ;which time, the line relays 79. and 80 of the connector E- are energized simultaneously and .the usualrelease circuitestablished. The bridge-cut-ofi relay, of the first-selector of the calledfline'doesnot energize-when the Tconnector calls back on the calling line, since the side-switch wiper 50 of the first-selector D is in third position, Howevenwhen' any 'oth'e'r ilineis called theQbridge-cut-ofl relay of the called line is bound to energize, as y =expl ained,as;s oonias a' connector side switch circuit is broken as soon as the connector ,r'eleases, thusf restoring the selector of the 'called line tothe control of the subscriber or subscribers thereof. 7 From th foregoing it will be, seen that I provide a dial-locking arrangement which is effective for .lockin out an intruding subscriber before the" cal ed subscriberanswers. In this way a calling subscriber on'a party line is safe against-interference after he has brou -ht the individual switch of theline to an o normal position, and beforethe called 'subscribe'r. answers. In other words, it. -isnot necessary forjthe called subscriber to answer in order to protect the calling subsubscriber ,on the same line; Furthermore. the dial-locking' arrangementis not operated by current which is put on the line for talking purposes, but to the contrary is dependpasses to third "position;- but the energizing v scriber against interference by some other fent upon" a special How of current in the.

party line, the current for talking purposes being supplied froml'ocal batteries. It wilL alsorbe seen that with-this arrangement the dial of a party properly in possession of the line is not locked, and that only the dial of the intruding subscriber becomes locked when he attempts to interfere with the first party in theuse of the line. As stated, however, an important feature of my present subscribers before the swers. Obviously,

"means responsiveto said calling dials,

adapted: for automatically eonnecti a5 'calhng subscriber with ;il1g device for each dial, each locking delocking device for each means responsive to the operation 01 .i a subscribers transmitter associated with '2.- In a telegphone exchange system, the v combination 0 scriber answers. a

' the 5. In a telephone exchal1g'e1systern, the

responsive to the operation of said dials, adapted for automatically connecting a call- 5 invention the locking outof intruding called subscriber an this is an important con-" sideration, because with such arrangement a calling party line subscriber is safe against interference practically as soon as he begins 1 using the line. Y i What I claim asmy invention is: 1. In a telephone exchange system, the combination of a telephone line, a plurality of subscribers calling dials on said line, said connecting subscriber,

dials, adapted for automatically a calling subscriber with a called each calling dial, a local battery for each transmitter, a locking device for each dial, and means for operating t-he'locking device of an intruding subscriber.

a plurality a telephone line,

said line,

of subscribers calling dials on a a called subscriber, a locking device for each dial, and means for operating the locking device of .an intruding subscriber before the called sub- In. a telephone exchange system, the com 'pation'of a telephone line, a plurality. of su 'cribers calling dials on said line, a locking device for each dial, means respon sive to tlie operation of said dials, adapted for automatically connecting a calling subscriber with :1 called subscriber, each locking device includingan'eleetromagnet, 11 normally open ground circuit for energizing each electroniagnehiand'means for closing ground circuit to energize the ma net and thereby lock thoidial of an intru ing subscriber. 1

4. In a telephone exchange system, the combination of a telephone line, a plurality of subscribers calling dials on said line, means responsive to the operation of said dials for automatically conmcting a calling subscriber with a called subscriber, a lockvice iiicluding -an electromagnet, a normally open ground circuit for energizing each magnet, each subscriber provided with a switch-hook controlling the ground circuit through his allotted electromagnet.

calling dials on I for each dlal, means responsive eratlon-of said dials, adapted for the said -individualewit'chis combination of a telephone mm a plurality of calling dials on saul telephone hne, means ing subscriber with :1 called sllhscl'il'ml', a

dial, adapted when operated to positively lock the dial against a rotation, and means for operating the locking of an intruding subscriber ns soon as the calling subscriber by operating his dial-sends in an initial impulse.

. 6. In a tele hone exchange system, the

combination of side thereof normally open, as lurality of said line, a'loe lling device to theopautomatia'telephone 11118, having one i cally connecting-a calling subscriber with a J called subscriber, and including means for closing the said normally'open side of the line as soon as the calling subscriber begins calling, andmeans for operating the look ing device of an intruding subscriber over a circuit including the said normally'open side 7. In a telephone exchange system,. the combinationfof a telephone lii1e,'an automatic switch'individual to said line, a plurality of calling dials o'n transmitting means responsive to the operation-of said dials, dial, andmeans for-operating the locking device of an intrudin subscriber as soon as 1n mal condition. r

8. In ;a tele "hone exchangesystem, the combination 0 :a'telephonelinqxa' lurality of calling dialsion saidjline,- imp se-transmitting means res onsi've to'the operation of said dials, a locliing device for-each dial, parallel circuits fprfoperating said 'lockmg devices, one side of all of said circuits, ingth'e circuit 0 interference. with the-subscriber possession of the line.'

9. A telephone exchange system comprisand each circuit includan intruding subscriber to prevent .ing a calling dial, a locklng device for said dial, said locking device includingan electromagnet, a normally open ground circuit for energizing said magnet, a switch-hook associated with the said dial, a telephone line, and means for closingsaid circuit by the operation of the switch-hook if the line is already in the possession of another subscriber.

10. In a telephone exchange system, the combination of a telephone line, a plurality of subscribers calling dials on said line, means including switches having vertical and rotary motion responsive to the o eration of said'dials. adapted for'automatically, connecting a calling'subsoriber with a called subscriber. trunk-release circuits therefor, a subscribers transmitter associated witheach calling dial, a local battery for each,transmittena locking device for each dial,'and means for operating the locking device of I an intruding subscriber.

11. In a telephone exchange/system, the combination of a telephone. line, a plurality of subscribers calling dials/on said line,

an oif-norground, and means for closing the i already in said line, impuls'ea locking device for each the line being common to means including switches having. vertical and rotary motion responsive tosaid calling dials, adapted for automatically connecting a calling subscriber with a called subscriber,

trunk-releasecircuits therefon'a locking devicefor each diahand means forfoperating the locking device of an intruding subscriber before the called subscriber answers.

locking device for .each dial, means includ mg swltches having vertical and rotary motron responsive I to the operation of said ;dials, adapted for automatically connecting a callingsubscriber with a called subscriber,

trunk-release circuits therefor, each locking devme including an electromagnet, a normally open ground circuit for energizing each electromagnet, and means for closing 1 the ground circuit to energizethe magnet and thereby lock the dial of an intruding subscriber. p

13. In a telephone exchange system, the

combination of a telephone line, a plurality of subscribers calling dials on said line, means including switches having vertical and rotary motion responsive to the operation of said dials for automatically connecting a calling subscriber with a called subscriber, trunk-release circuits therefor, a

' locking device for each dial, each locking device including an electromagnet, anor-v mally open ground circuit for energizing 5 each magnet, each subscriber provided with a switch-hook controlling theground cir cui't through his allotted electromagnet.

.14. telephone exchange system, the combination ofa telephone line, a plurality of-calling dials on said telephone line, means including switches having vertical and r0 tary motion responsive 'to the operation of sard dmls, adapted for automatically connecting a calling subscriber with a called 4 subscriber, trunlnrelease' circuits therefor, a

locking device for each dial, adapted when operated to pos tively lock the dialagainst rotation, and means for operating the lockmg dev1ce of an lntruding subscriber as soon a thecall1ng subscriber by operating his ial sends in an initial impulse.

15i-In a telephone exchange system, the combination of a telephone line having-one side thereof normally open, a lurality of calling dials on said line, a 100 in" device for each dial, means including switches having vertical and'rotary motion responsive to the operation of said dials, adapted for automatically connecting a calling subs'criber with a called subscriber, and 1ncluding means for closing the said normally open side of the line as soon as the calling subscriber begins calling, trunk-release circuits therefor, and means for operating the locking device: ofan intruding subscriber over acircuitincluding thesaid normally eration of said dials, trunk-release circuits therefor, a' locking device for each dial, and;

means for operating-the locking device of an "intruding subscriber as soon as the said individual switch is in an ofienormal condition. i Y

17. In a telephone. exchange system,- the combination of a telephone line, a plurality of. calling dials on said line, means having first one motion to select groups and then rotary motion to connect with a line in-the selected group responsive to the operation of said dials, trunk-release circuits therefor, alocking device for each dial, parallel circuits for operating saidlocking devices, one side of the line being common to all of said circuits, and each circuit including thein "the selected group responsive to the opground, and means for closing the circuit of an intruding subscriber to prevent interference with the subscriber already in possession of the line. i 18.- A telephone exchange system comprising a calling dial, means responsive theretohaving a straight motion to select groups and a rotary motion to connect with a line in theselected group, a locking .device for said dial, said locking device including an electromagnet, a normally open ground circuit for energizing said magnet, a

switch-hook associated with the said dial, a I

telephone line, and means for closing said circuit by the operation of the switch-hook if the line is already in the possession of another subscriber.

19. In a telephone trunking system, subscribers lines divided into groups, the combination of a telephone line, a plurality of subscriberscalling dials on said line, means responsive to the operation of said dials having first vertical motion to select groups and then-rotary motion to connect with a line in any predetermined group, adapted for automatically'connectin a calling subscriber with a called-subscrl er, a subscribers transmitter associated-with each calling dial, a local battery for each transmitter, a. locking device for each dial, and means for operating the lockingrdevice of an intruding subscriber.

20. In atelephone trunking system, subscribers lines divided into groups, the combination of a telephone line, a plurality of subscribers calling dials onsaid line, means responsive to said calling dials having first bination of a telephone line,

'scribers lines z with a called subscriber,

vertical motion to select groups and then rotary motion to connect with a line in any predetermined group, adapted for automatically. connecting a calling subscriber with a called subscriber, a locking device for each dial, and means for operating the locking device of an intruding subscriber before the called subscriber answers.

21. In a telephone trunking system, subdivided into groups, the combination of a telephone line, a plurality of subscribers calling dials on said line, a locking.device foreach dial, means responsive to the operation of said dials having first vertical motion to select groups and then rotary. motion to connect with a line in any predetermined group, adapted for automatically connectinga calling subscriber each locking device including an electromagnet, a normally open ground circuit for energizin each clectromagnet, and means for closing the ground circuit to energize the magnet and thereby lock the dial of an intruding subsomber.-

22. In a telephone trunking system, subscribers lines divided into groups, the coma plurality of subscribers calling dials on said line, means responsive to the operation having first vertical motion to select groups and then rotary motion to connect with a line in any predetermined group, adapted for automaticallv connecting a calling subscriber with a called subscriber, a locking I device for each dial, each locking device into (positively lock an eluding an electromagnct, a normally open ground circuit for energizing each magnet, each subscriber provided with a switch-hook controlling the ground circuit through his allotted electroinagnet.

23. In a telephone trunking system, subscribers lines divided into groups, the combination of a telephone line, a plurality of calling dials on said telephone line, means responsive to the operation of said dials having first vertical motion to select groups and then rotary motion to connect with a line in any predetermined group, adapted for automatically connecting a calling subscriber with a called subscriber, a locking device for each dial adapted when operated the dial means for operating the locking device of an intrudin subscriber as soon as the calling subscriber by operating his dial sends in an initial impulse.

24.-In a telephone'trunking system, subscribers lines divided into groups, the combination of a telephone line having one side thereof normally open, a plurality of calling dials on said line, a locking. device for each dial, means responsive to the operation of said dials having first vertical motion to against rotation,

of said dials I l i 1 switch individual to said line, a plurality of calling dials on said line, means responsive to the operation of said dials having first vertical motion to select groups and then rotary motion to connectwith a line in any predetermined group, a locking device for each dial, and means for operating the locking device of an intruding sub scriber as soon as the said individual switch is in an off normal condition.

In a telephone trunking system, subscribers lines divided into groups, the combination of a telephone line, a plurality of calling dials on said line, means-responsive to the operation of said dials having first vertical motion to select groups and then rotary motion to connect with a line in any predetermined group, a locking device for each dial, parallel circuits .for operating said locking devices, one side of the line being common to all of said circuits, and each circuit including the ground, and means for closing the circuit of an intruding subscriber to prevent interference with the subscriber already in possession of the line.

27. In a telephone trunking system, lines divided into groups, a plurality of calling dials, a locking device on each dial, a selector switch having motion in one plane to select groups and then motion in-a plane at right-angles thereto to select a line in any predetermined group, said switch being responsive to the operation of said dial, a side switch for said selector switch having three operative positions, and means for o crating said locking device when said side switch is in its first, second or third position, substantially as described.

28. In a telephone divided into groups, a plurality of calling dials, a locking device on each dial, a selector switch and a connector switch having motion in a plane to select groups and then motion in a plane at right-angles thereto to select a line in any predetermined group, said connector switch being responsive to the operation of said dial, a side switch for said connector switch having three operative positions, and means for operating said trunking system, lines normally open side dials for each of said lines, a locking device for each dial, an automatic switch, a side switch therefor, and means for operatingsaid locking device when the side switch is 10 in any one of its operative positions,substantially as described.

' 30. In a telephone system, a switch hook,

a calling dial, and a lookin magnet therefor adapted to be energized as soon as the switch hook rises by establishing a circuit 15 from ground to the line, substantially as described.

Signed by me at Chicago, Cook county, Illinois, this 20th day of February,

WILSUN L. CAMPBELL.

Witnesses:

J. NORBY, ARTHUR B. SPERRY.

00,101 at this potent may be obtained for be out; euhfby addressing the Oommfiasieaer of masts,

Wouldn't, D. G." 

